In the related art, in the case in which work such as handling or the like is performed in accordance with the position and the orientation of a large object such as a vehicle body being conveyed by a conveyor, images of three known gauge marks provided on the object are individually captured by using three cameras, and the position and the orientation of the object are three-dimensionally measured from the positional relationship of the acquired three known gauge marks (for example, see Japanese Unexamined Patent Application, Publication No. Hei 7-13613).